As a distance between a positive (P) electrode and a negative (N) electrode of a LED flip chip is around 75˜150 micrometers (μm), in a conventional design of ceramic package substrate used in a flip chip technique, when performing reflow soldering after die bonding and/or when the LED flip chip package structure undergoing a second reflow soldering of a back-end surface mounted technology (SMT) process, a short-circuit phenomenon may be easily occurred resulting from solders melting and flowing, which would result in the LED malfunction.
Specifically, referring to FIG. 1, it is a structural view of a conventional LED flip chip package structure. As shown in FIG. 1, a LED flip chip package structure 10 includes: a ceramic substrate 11, soldering pads 12a, 12b, metal-filled holes 13, electrodes 14a, 14b, a LED flip chip 15, a bowl-shaped structure 18 and a fluorescent glue 19. The soldering pads 12a, 12b are disposed on an upper surface of the ceramic substrate 11 and spaced from each other, the electrodes 14a, 14b are disposed on a lower surface of the ceramic substrate 11 and spaced from each other, the soldering pads 12a, 12b respectively are electrically connected to the electrodes 14a, 14b by the metal-filled holes 13. The LED flip chip 15 is disposed with a positive electrode 151 and a negative electrode 153, and the positive electrode 151 and the negative electrode 153 respectively are electrically connected to the soldering pads 12a, 12b by solders 16. The bowl-shaped structure 18 is disposed on the upper surface of the ceramic substrate 11 and surrounding the LED flip chip 15. The fluorescent glue 19 is disposed in the bowl-shaped structure 18 and covering the LED flip chip.
Referring to FIG. 2, it is a microscopic photograph showing the soldering pads in the LED flip chip package structure shown in FIG. 1. As seen from FIG. 1 and FIG. 2, it can be found that since a distance between the soldering pads 12a, 12b is relatively short, during a reflow soldering process, the solders 16 would be melted and flow into a region between the soldering pad 12a and the soldering pad 12b and thereby cause the soldering pad 12a and the soldering pad 12b to be electrically connected with each other, as a result, a short-circuit phenomenon as shown in FIG. 2 would be occurred.